Exhaust system and engine provided with the same

Abstract

An exhaust system comprises a first exhaust manifold connected to a first exhaust port of a cylinder; a second exhaust manifold connected to a second exhaust port of the cylinder; a variable valve lift apparatus controlling a valve that closes and opens the first exhaust port; an after-treatment apparatus connected to the first exhaust manifold and the second exhaust manifold; an exhaust temperature sensor; and a controller controlling the variable valve lift apparatus based on an output signal of the exhaust temperature sensor.

What is claimed is: 
     
         1 . An exhaust system comprising:
 a first exhaust manifold connected to a first exhaust port of a cylinder;   a second exhaust manifold connected to a second exhaust port of the cylinder;   a variable valve lift apparatus controlling a valve that closes and opens the first exhaust port;   an after-treatment apparatus connected to the first exhaust manifold and the second exhaust manifold;   an exhaust temperature sensor; and   a controller controlling the variable valve lift apparatus based on an output signal of the exhaust temperature sensor.   
     
     
         2 . The exhaust system of  claim 1 , wherein the controller controls the variable valve lift apparatus in a normal operation state when a temperature of an exhaust gas is higher than a predetermined reference temperature. 
     
     
         3 . The exhaust system of  claim 2 , wherein an operation mode of the variable valve lift apparatus comprises a normal mode and a CDA operation mode. 
     
     
         4 . The exhaust system of  claim 2 , wherein:
 the after-treatment apparatus comprises a catalyst; and   the predetermined reference temperature is based on an activating temperature of the catalyst.   
     
     
         5 . The exhaust system of  claim 1 , wherein:
 the controller controls the variable valve lift apparatus in a deactivated state when an engine starts; and   the controller controls the variable valve lift apparatus in a normal operation state when a temperature of an exhaust gas is higher than a predetermined reference temperature.   
     
     
         6 . The exhaust system of  claim 5 , wherein an operation mode of the variable valve lift apparatus comprises a normal mode and a CDA operation mode. 
     
     
         7 . The exhaust system of  claim 5 , wherein:
 the after-treatment apparatus comprises a catalyst; and   the predetermined reference temperature is based on an activating temperature of the catalyst.   
     
     
         8 . An engine comprising:
 a first exhaust manifold connected to a first exhaust port of a cylinder of the engine;   a second exhaust manifold connected to a second exhaust port of the cylinder of the engine;   a variable valve lift apparatus controlling a valve that closes and opens the first exhaust port;   an after-treatment apparatus connected to the first exhaust manifold and the second exhaust manifold;   an exhaust temperature sensor; and   a controller controlling an operation of the variable valve lift apparatus based on an output signal of the exhaust temperature sensor.   
     
     
         9 . The engine of  claim 8 , wherein an operation mode of the variable valve lift apparatus comprises a normal mode and a CDA operation mode. 
     
     
         10 . The engine of  claim 9 , wherein the controller controls the variable valve lift apparatus in the normal mode when a temperature of an exhaust gas is higher than a predetermined reference temperature. 
     
     
         11 . The engine of  claim 10 , wherein:
 the after-treatment apparatus comprises a catalyst; and   the predetermined reference temperature is based on an activating temperature of the catalyst.   
     
     
         12 . The engine of  claim 9 , wherein:
 the controller controls the variable valve lift apparatus in the CDA operation mode when the engine starts; and   the controller controls the variable valve lift apparatus in the normal mode when a temperature of an exhaust gas is higher than a predetermined reference temperature.   
     
     
         13 . The engine of  claim 12 , wherein:
 the after-treatment apparatus comprises a catalyst; and   the predetermined reference temperature is based on an activating temperature of the catalyst.